<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>javascript</title>
    <script type="text/javascript">
    var a="das",
        b=100,
            c=true;
        alert(a);
        alert(typeof c);//打印数据类型
        alert(Number.MAX_VALUE);

    </script>
</head>
<body>

</body>
</html>